So how does a parent or teacher really know when a child can't see the board clearly? A kid with less than optimal vision will probably tell you he sees fine.
"They really don't know what they're missing because they can't see what's normal," said Dr. Elise Brisco, an optometrist at the Hollywood Vision Eye Care Center.
She says she detects many vision problems missed during ordinary school exams.
"I'll have parents come in who have children with serious vision problems, who are not doing well in school and they'll say, 'But I had my eyes checked at the pediatrician's office,'" said Dr. Brisco. "It gives you a false sense of confidence."
Studies show 60 percent of problem learners may actually have a vision problem and the signs and symptoms are easy to miss.
"Some of the symptoms of vision problems would be a child who's rubbing their eyes whenever they read. They're uncomfortable doing any sort of visual or desk task or working on the computer. These are also the kids who know the material well verbally but they don't test well," said Dr. Brisco.
Kids who are 8 or 9 years old should not be using their fingers to read. It could be a sign your child's eyes don't work well together. Another sign is if your child is having trouble catching a ball.
"A child who is having trouble catching a ball, their timing's off, they're a little clumsy, these are the kids who are not picked to be on the team," said Dr. Brisco. "So many of those kids have a vision problem that is correctable but it needs to be detected first."
That's why Dr. Brisco recommends kids get annual comprehensive eye exams. Your child may not have a problem this year, but she says young eyes are always changing.
Dr. Brisco says if you can't afford a yearly exam with an optometrist, many offices do offer free services.